This spray-on concrete helps old buildings last during an earthquake

A team of civil engineers in Canada has developed an environmentally friendly spray-on concrete that can help structures weather an earthquake without damage.

Researchers at the University of British Columbia (UBC) have successfully tested an eco-friendly ductile cementitious composite (EDCC) under extreme conditions, including shocks similar to the 9.0-magnitude earthquake that shook Japan in 2011.

Before testing, interior walls were sprayed with a 10 mm-thick layer of EDCC, said researcher and civil engineering lecturer Salman Soleimani-Dashtaki.

“We then subjected them to Tohoku-level [Japan] quakes, and other types and intensities of earthquakes — and we couldn’t break them,” he said.

EDCC might be of particular use in earthquake-proofing older buildings, as well as pavements and pipelines. The material will be used to ‘seismically retrofit’ a Vancouver primary school later this year, followed by a school in a high-risk area of India.

The material is not only sturdy, but also more environmentally friendly. It uses fly ash to replace 70 per cent of the concrete, recycling an industrial by-product to reduce the amount of concrete used. Fly ash and polymer-based fibres were combined with concrete to give the material similar structural properties to steel.

According to Professor Nemkumar Banthia, who supervised the research team, this kind of swap is an urgent requirement to reduce carbon emissions.

“One tonne of cement production releases almost a tonne of carbon dioxide into the atmosphere, and the cement industry produces close to 7 per cent of global greenhouse gas emissions,” he said.

Australia is moderately seismically active, and earthquakes pose the greatest risks to heritage buildings with unreinforced masonry or buildings constructed before the 1990s, which were not designed to withstand large earthquakes. These buildings are susceptible to earthquake damage due to their age as well as structural weaknesses.

Geoscience Australia researcher Mark Edwards said that buildings designed to current standards would generally travel quite well through a magnitude-5 earthquake. However, in 2013 following the 3.5-magnitude earthquake in southwestern Sydney, global insurer GBE announced earthquakes in this area posed the highest risk to its Australian business, with possible losses of up to $20 billion.

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Nadine Cranenburgh is an electrical engineer with postgraduate qualifications in environmental engineering, and professional writing and editing. She works as a freelance writer and editor specialising in complex topics that draw on her experience in the engineering, local government, defence and environment industries.

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